docs: def get_f_code_idx():
      """
      How many pointers into PyFrame is the ``f_code`` variable?
      """
      frame = sys._getframe()
      frame_ptr = id(frame)
  
      LARGE_ENOUGH = 20
  
      # Look through the frame object until we find the f_tstate variable, whose
      # value we know from above.
      ptrs = [ctypes.c_voidp.from_address(frame_ptr+i*svp)
              for i in range(LARGE_ENOUGH)]
  
      # Find its index into the structure
      ptrs = [p.value for p in ptrs]
  
      fcode_ptr = id(frame.f_code)
      try:
          threadstate_idx = ptrs.index(fcode_ptr)
      except ValueError:
          log.critical("rootpy bug! Please report this.")
          raise
      return threadstate_idx